1. Field of the Invention
The present invention relates to a process for the incremental enrichment of deuterium and/or tritium in a material which is suitable for the isotope exchange of deuterium and tritium with hydrogen, as well as to an apparatus for the implementation of the process.
The formation of deuterium, D.sub.2, and tritium, T.sub.2, is not only of significance in the area of nuclear fusion technology, in which deuterium and tritium serve as "fuels" and which are fused to helium with the output of energy. It is also known to utilize deuterium in nuclear reactors moderated with heavy water, in which D.sub.2 O is employed as the moderator. Tritium is used in the production of luminescent pigments, for example, luminescent paints, as well as being a component of gas filled fluorescent lighting tubes and in the production of lightning arresters. Moreover, tritium is employed as a target for beam modulation in particle accelerators. In addition thereto, tritium is useful for the radioactive labeling of chemical compounds, for example, in the field of biochemistry.
Deuterium is contained in basic hydrogen and in water at a level of 0.015 At %. In hydrogen it is in the form of HD and in water it is in the form of HDO. Tritium is present in basic hydrogen only in very low concentrations. However, it can be obtained, for instance, as a byproduct during the operation of nuclear reactor installations, particularly heavy water reactors and high-temperature reactors, as well as during the reconditioning of spent nuclear fuel elements. Inasmuch as tritium is radioactive and is directly absorbed in the bio-cycle in the form of HTO, even the minute quantities of tritium which are produced during the neutralizing of nuclear reactor installations cannot be ignored. Thus, in order to neutralize the thus generated tritium, it is known to enrich and bond the tritium in water.
2. Discussion of the Prior Art
Different processes are known for the enrichment of deuterium or tritium in hydrogen and water, such as those disclosed by K.M. Mackay et al "Deuterium and Tritium", in "Comprehensive Inorganic Chemistry", Volume 1, Pergamon Press, New York, 1973, pages 77 through 84; as well as NUKEM 500, "Herkunft, Handhabung and Verbleib von Tritium" RSI-510 321/196-SR 165, February 1980. For example, an enrichment is achieved through the distillation of liquid hydrogen at a temperature of about 23.degree. K. or through the distillation of water at 70.degree. C. and under a vacuum. Hydro-electrolysis is also useful as such an enrichment process, providing a high separation factor. However, when using a hydro-electrolysis process, as also a process involving the distillation of hydrogen, one must meet increased safety demands (due to the need for a high degree of sealing and explosion protection), and one must also contend with significant energy demands with regard to the enriched quantity of deuterium or tritium. The latter problem of energy requirements arises due to the need to start with a low initial concentration of the deuterium and tritium in the water. In addition thereto, there are also processes known in which deuterium and tritium are enriched in water through an isotope exchange in the liquid phase, as disclosed by H.J. Fiek et al, "Tritium-Anreicherung durch Isotopenaustausch zwischen Wasserstoff und Wasser, mittels hydrophoben Katalysators fuer die Kernbrennstoff-Wiederaufbereitung", Chem.-Ing.-Techn. 52, 1980, pages 892 through 895. However, the exchange speeds in such a process are relatively slow, even with the utilization of catalysts. Moreover, currently known catalysts evidence a high susceptibility to disruption.
A heavy water recovery through the utilization of ammonia, NH.sub.3, is mentioned in KWU-Report, No. 32, April 1980, page 9. The heavy water is recovered through a monothermal ammonia-hydrogen isotope exchange. In such a process, however, disadvantages arise from the high energy demands, which are generated during the electrolytic ammonia fission process which is used and which are also required for the subsequent ammonia synthesis. Also the yield for the exchanged deuterium remains low during an ammonia-water isotope exchange.